Studies probe the very beginnings of root growth
José Dinneny, 39
Plant stress biologist
Carnegie Institution for Science
“They’re able to integrate information and make coherent decisions without a nervous system, without a brain,” he points out. Plus, plants find water without sight or touch. For too many of us, however, lawns, salads and pots on a sunny windowsill make plants so familiar we’ve become blind to how exotic they are.
“We’re out searching the solar system and the galaxy for extraterrestrial life,” says Dinneny, 39, “and we have aliens on our own planet.”
The thrill of discovering plants’ alien ways drives Dinneny to explore how roots search for water. His research group, at the Carnegie Institution for Science labs in Stanford, Calif., “runs on curiosity,” he says.
His work could have practical food security and geopolitical consequences. Dinneny is passionate about the molecular whys and hows of regulating plant growth. From a background in basic plant development, he moved to questions of environmental stress. These questions are important in “this huge crisis we face as a species,” says Jonathan Lynch, a root biologist at Penn State and the University of Nottingham in England. Knowing how to grow plants in environments degraded by climate change will be crucial to feeding an exploding human population.
Lynch calls Dinneny “one of these transitional characters, very important in science.” He builds bridges between the pure molecular biologists and the more agricultural plant biologists, “people like me who think about specific plants,” Lynch says. The two groups rarely mingle and focus on different goals and priorities, Lynch says. He remembers a 2015 workshop on plant development and drought stress that Dinneny helped organize: “People were standing up and shouting.”
To add a touch more agricultural realism to molecular root research, Dinneny and colleagues have developed a new alternative to the typical seedlings in petri dishes. The system, called GLO-Roots, makes roots in soil easier to watch. Plant roots induced to glow spread in slim sandwiches of soil between two clear plates, weaving among air pockets, micro rivers and clots of dirt. Computer analysis of images tracks where root tissues luminesce as various genes turn on in the twinkling underground observatory, giving researchers clues to how roots detect and respond to their environment.
Thrusting out a side branch to seek out water turns out to be a local matter on a root, Dinneny and colleagues found using micro-CT scans of roots in soil. Analyzing hormones showed that the tissues can sense water differences on a scale of mere micrometers. The team described the basic development of what Dinneny calls “hydropatterning” in 2014 in Proceedings of the National Academy of Sciences.
“Myself and many other people had studied lateral roots for many years,” says Malcolm Bennett of the University of Nottingham, who collaborated on the study. It was familiar to see seedlings forming roots mostly on the wet side. But Dinneny thought to ask how something so obvious was actually happening.
Now he and colleagues are probing deeper into the cellular machinery at work. Individual cells in the root need to be expanding to detect water, he and Carnegie colleague Neil E. Robbins II proposed online in January at bioRxiv.org.
Plants are very different from vertebrates, which develop while shielded in wombs or eggs. Root branching responds to outside triggers, heading toward life-sustaining reservoirs.
In a different world, Dinneny says, his job might have been cooking plants instead of studying them. He can “make a mean potpie” and enjoys the nightly challenge of preparing a meal that his three children “find edible.” His maternal grandfather’s cooking in the 1950s at a resort in Acapulco, Mexico, impressed a visitor who hired his grandparents as at-home cook and maid. That meant a move to southern California, and eventually a chef position for the grandfather in a Los Angeles restaurant.
Dinneny spent much of his childhood in California’s San Fernando Valley. “I wasn’t tracked to do anything excellent at all,” he says of his school years. “I was placed in classes that weren’t particularly challenging.” In 10th grade, though, he took an Advanced Placement biology class and still remembers a pivotal moment when his teacher asked about a chemical bond in DNA. “I was the only person who raised his hand.” The answer: a phosphodiester bond. “Everyone looked around the room sort of wondering who could possibly have known that factoid,” he says.
He was surprised himself, and began to realize he had a talent for understanding biology. He lobbied hard to transfer to advanced classes and began to apply himself to studying. He didn’t come from an academic family, but he had fine examples of working hard, including his single mother, a government accountant.
“Often we kind of cubbyhole ourselves into, ‘OK, I’m good at this,’ or ‘I’m not good at that.’ Or they’re doing well because they’re just inherently better at doing this than I am,’” he says. “There is a magical relationship between effort and success.” Not every goal gets met, but “you’re going to do better than you ever thought.”
By his senior year, Dinneny was a straight A student headed to University of California, Berkeley. There, a holistic approach to plant science captivated him. For his Ph.D., at the University of California, San Diego, he studied the genetics of plant development, then moved to studying plants under environmental stress.
Deep-sea creatures and ocean exploring had captivated him for much of his childhood. But plants have turned out to be strange enough.
Y. Bao et al. Plant roots use a patterning mechanism to position lateral root branches toward available water. Proceedings of the National Academy of Sciences. Vol. 111, June 24, 2014, p. 9319. doi: 10.1073/pnas.1400966111
D. Dietrich et al. Root hydrotropism is controlled via a cortex-specific growth mechanism. Nature Plants. Vol. 3, May 8, 2017, 17057. doi: 10.1038/nplants.2017.57.
S. Milius. Changing climate could worsen foods; nutrition. Science News. Vol. 191, April 1, 2017, p. 14.